1. Field of the Invention
This invention generally relates to a touch system and, more particularly, to an optical touch system for detecting multi-touch gesture and an object detection method therefor.
2. Description of the Related Art
In recent years, the touch panel has been widely applied to various electronic devices due to its convenience, and the optical touch panel is especially favored by designers as it can be used for multi-touch operation.
Please refer to FIG. 1A, it shows a conventional optical touch panel 9, which includes two image sensors 91 and 91′, invisible light sources 92 and a touch surface 93. When two fingers 8 and 8′ are close to the touch surface 93, the image sensors 91 and 91′ can respectively acquire an image window W91 and W91′ as shown in FIG. 1B. The image windows W91 and W91′ contain shadows I8 and I8′ of the fingers 8 and 8′ from blocking the light sources 92 and background images BI, wherein as the background images BI in the image windows W91 and W91′ are corresponding to the image of the light sources 92, they have a higher brightness. A processing unit (not shown) can generate a 2-dimensional plane space corresponding to the touch surface 93 according to the image windows W91 and W91′, and calculate positions of the fingers 8 and 8′ on the 2-dimensional plane space according to one-dimensional positions of the shadows I8 and I8′ in the image windows W91 and W91′.
However, when one of the fingers 8 and 8′ blocks the other with respect to the image sensors 91 and 91′, for example as shown in FIG. 2A, the image windows acquired by the image sensors may have different numbers of shadows; for example, the image window W91 acquired by the image sensor 91 contains two shadows I8 and I8′ but the image window W91′ acquired by the image sensor 91′ contains only one merged shadow I8+I8′. As a result, the processing unit is not able to calculate correct positions of the fingers 8 and 8′ on the 2-dimensional plane space according to the shadows I8, I8′ and I8+I8′.
Accordingly, the present invention provides an optical touch system capable of acquiring image windows having brightness information and image features. The optical touch system may identify an object range according to the image windows having the brightness information and distinguish the objects blocking each other according to the image windows having the image features thereby increasing the accuracy of object positioning.